For a variety of different reasons, oil wells are often not perfectly vertical. Meandering or deviated well bores cause engagement of the sucker rod with the inner wall surface of the production tubing string causing wear to the tubing string through movement of the sucker rod. After a length of time, the sucker rod will either wear through the side of the tubing string or reduce it to a point of failure under load.
To reduce the effects of wear caused when a sucker rod comes into contact with the inner surface of the tubing string, others have developed tubing rotators which slowly rotate the tubing string about the sucker rod to more evenly distribute wear around the inside circumference of the tubing string.
Although such rotating devices have been proven to be an effective means for extending the life of a tubing string, their use has resulted in additional production difficulties. First, tubing rotators are typically threaded onto the upper end of the tubing string thereby making it necessary to "lift" the entire string in order to service the rotator. Secondly, in deviated wells the tubing string may be subjected to nonvertical loading resulting in excessive frictional wear between the tubing string and the sucker rod, particularly toward the bottom of the tubing string. Furthermore, existing rotator and tubing string structures are commonly prone to "blow-back" wherein fluids are driven upwardly between the well casing and the tubing string resulting in leakage at the wellhead or loss of well control.